Fuel of the Week: Carbon

carbon small

As most of you know by now, the Neumann Drive was primarily invented by an Australian physics PhD student, Patrick Neumann. The question therefore came up on the interwebs, with particular props to fatblonde and WittyOriginalName of Reddit, as to whether it can run on Vegemite and/or beer.

One of the great things about the Neumann Drive is it uses a variety of fuels. Unfortunately, because the drive needs a vacuum in order to work, both beer and Vegemite would get very, very messy if used as a fuel. That said, as proud Australians, we believe strongly that beer does belong in space. We just don’t want to waste it on fuel.

However, and this a big however, it can work on both used beer and used Vegemite, if these are properly reduced down to their constituent carbon, and that carbon is sintered into a fuel rod that can fit one of the mostly-tungsten trigger wires.
In bench-top tests in our laboratory rig, carbon can achieve a specific impulse of 4100 using four 60-joule pulses, each 300 microseconds long. We can pulse the carbon four times per second to deliver just under 4 milliNewton seconds during that second. So, using carbon, you need just over 250 seconds of operation to deliver a Newton-second of impulse.

As they get worn down by use, these sintered fuel rods do tend to lose structural strength and have a tendency to break apart after a large number pulses, which will probably mean pulling half-used fuel rods out of the drive to be ground down and then re-sintered, but if you’re getting fuel from a carbonaceous asteroid, or from carbonising used Vegemite from astronaut waste products, then this may be less of a concern than otherwise.

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